Continental IO-520 lifter cam spalling

I represent 2 U206G’s (1982 and 1983), an A185F (1976) and a 1976 C310R each with factory spec, normally aspirated IO 520 engines. Since 2012 there have be repeated cases of spalling lifters, 4 of which have damaged the cam. 4 of these cases have been factory rebuilt engines. 2 of these shredded enough metal to impregnate particles into the oil pump housing and cause diminishing oil pressure. In the process we have begun the use of Camguard products along with oil analysis. No improvement seems to have occurred. This is no criticism against Camguard since they have gone out of their way to help.The cost of course is overwhelming. Consultations with Continental, Ram, Aircraft Specialties have proven inconclusive. To avoid further damage we implemented visual lifter and cam inspections every 200 hours of operation which is more invasive than desired. In each case this removal inspection has yielded lifters which have shown spalling and required exchanging.Related data: Oil changes at 50 hours or lessType oil: From 2012 until 2016 Phillip XC20W50, presently Exxon Elite to try something differentHours of operation: 200 to 300 hours annuallyEngine preheaters are used during sub-freezing temperaturesCruise setting: 65%Type of operation: Flight school training

We have found the use of multi-viscosity oils to cause more of this kind of issue since their introduction.

Think of it this way, the 20w50 oil behaves like a 20 weight oil and drains off the engine parts more quickly if the engine has been sitting. Think of how many of your customers have 'low time' engines that are 25 years old, corrosion plays a big part in the failure of components in these engines rather than mechanical wear. Thicker oils coat the surfaces for longer during storage so that the pitting corrosion of the cam and lifter surfaces or spalling and wear due to the pitting isn't as big a factor.

We only recommend W100 (50 weight oil) or W80 (40 weight) for winter operation in our engines and haven't had as many of these issues.

A small update: a month ago we removed the lifters after 200 hrs of operation in one of 3 of our engines (in a C-185)which now was outfitted with all OH'd lifters from Aircraft Specialties. This time all 12 passed without replacing any after 200 hours of operation. In a few Next week we'll be inspecting one of our C206's which is approaching the 200 hr mark as well. I'll try to keep you updated.

I want to inform of our progress with the lifter and cam wear that we have been experiencing. As you recall it was occurring on IO-502’s installed on a C-A185F and 2 U206G’s. These 3 engines had experienced lifter wear to the extent that required cam replacement and in one case an engine replacement. After the related teardowns and replacement each engine received new Continental and Superior lifters. After the following 200 hours of operation they as well showed significant levels of pitting requiring complete lifter replacement. It was decided that OH’d lifters from Aircraft Specialties be installed at that point and at a follow-up inspection at another 200 hours, the lifters were 100% good of all 3 engines. None needed replacement.

We are that convinced that the 200 hour repetitive inspection is no longer needed. As a step of precaution we will be extending the inspection to every 400 hours. At that point we’ll review their condition.

We've always suggested 100w oil in summer and 80w in winter as we have had issues with corrosion (if not run regularly as stated in a previous reply) and if an engine is running hot it may break down multi-viscosity oils.

What are you typically running for oil temps and CHTs in these aircraft?

To state that a 20W50 oil “behaves” like a 20 weight oil is just plain wrong. The “20” in 20w50 refers to the oil’s COLD characteristics. Specifically, it refers to the length of time required for a standard quantity of said oil to gravity flow through a standard sized orifice at zero degree Fahrenheit. The lower the number the quicker it flows. So, a 15w50 oil is thinner at zero degrees than a 20w50 oil. The “50” in 20w50 refers to the oil’s HOT characteristics as compared to a straight weight oil. A 20w50 oil will get no thinner when hot than straight 50 weight oil. A 5w40 oil would not get thinner than a straight 40 weight and yet still flow quite well at zero degrees. This is all possible because of polymer physics.

The company I work for has operated IO520s on a fleet of several dozen aircraft for decades using only Aeroshell single grade oils and we have always had a certain amount of cam/lifter issues. It seems more likely to occurs on low time/mid time engines, but there are always exceptions. When we put 80 hours a month on the engines the problem was definitely less than it is now that we put 25 or 35 hours a month on them. My opinion is that the hours flown will have a much larger effect on the cam’s health than the type of oil used will have on it.